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Apr 23, 2011

Macro Photo

Taking close-up pictures of small things is called "macro photography." I have no idea why. Perhaps because the small things in macro photography are generally larger than the things you are taking pictures of when doing "micro photography". If you really want to be pedantic then you should say you are doing "photomacrography".

What Kind of Camera

Point and shoot digital cameras can have remarkable macro capabilities, but for best results you want a single-lens reflex camera. These allow you to attach special-purpose macro lenses and show you in a bright optical viewfinder what you will get on the sensor.
A typical setup might be a Canon Digital Rebel XTi with a Canon EF-S 60mm f/2.8 Macro USM . This lens is designed for the small-sensor Canon cameras and gives a working distance equivalent to 100mm on a full-frame photo camera. The lens is specified to focus down to "1:1" or "life size". This means that the smallest object you can photograph that will extend to the corners of the final digital photo will be the same size as the sensor inside the Canon Rebel camera, 15x22mm. A professional photographer might use Canon EOS 5D and a lens designed for full Canon EF 100mm f/2.8 Macro USM. Confusingly, this lens is also specified to focus down to "1:1", but this time the sensor is 24x36mm in size, the old 35mm film standard. So you can't take a photo of something quite as small as with the cheaper equipment.
In the film world, the 35mm photo camera systems had comprehensive range of macro lenses and accessories and some medium format systems, such as the Rollei 6008 would have at least a few lenses and extension tubes. Only the extremely patient ever did macro photography with a 4x5 inch view photo camera.

Close-Up Lenses

Your eyes don't focus so great on really small things either. Do you try to pull your cornea a foot away from your retina? No. You stick a magnifying glass in front of your cornea. You can do the same thing for your normal lens. Unlike your cornea, it even has convenient threads for attaching a magnifying glass. The magnifying glass screws into the same place where a filter would go.

Macro Lenses

The best macro lenses are the latest autofocus mount models made by Canon and Nikon, typically in focal lengths ranging from 50 to 200mm. Each lens will focus continuously from infinity to 1:1. You can shoot the moon and capture the bear claw without stopping to change lenses or screw in filters. How do these lenses work? Do they just have a much longer helical than the 50mm normal lens? Yes and no.

Macro Zoom Lenses

Macro zoom lenses are not macro lenses. They don't allow significantly greater magnification than a 30mm or 50mm normal lens and they deliver low quality.

Exposure

Unless you are using close-up lenses, when doing any kind of macro work, you always have to consider the effective f-stop. Even if you are using the SLR body's built-in meter, which will correct automatically for light loss, you can't turn off your brain. Why not? Because the effective aperture affects picture quality.
Taking pictures through a pinhole results in tremendous depth of field but very low sharpness due to diffraction. This is why lenses for a 35mm film camera stop at f/22 and don't go to f/45 or f/64. Large format camera lenses provide these smaller apertures for two reasons: (1) the lenses are longer (f/64 on a 210mm lens is not all that small a hole); (2) the negative won't be enlarged very much.
If you're at 1:1 and have selected f/22 on the macro lens barrel, you need to look at the lens markings and/or the close-up exposure dial in the Kodak Professional Photoguide to learn that your effective aperture is f/45.
If you're using a handheld meter, you absolutely must use these corrections (e.g., meter says f/22 but you're focussed down to 1:1 so you set f/11 on the lens barrel).

Lighting

A good quick and dirty lighting technique is to use a through-the-lens (TTL) metered flash with a dedicated extension cord). A modern handheld flash is extremely powerful when used a few inches from a macro subject. That lets you stop down to f/16 and smaller for good depth of field. You can hold the flash to one side of the subject and have an assistant hold a white piece of paper on the other side to serve as a reflector. If you want a softer light, you will have enough power in the flash to use almost any kind of diffusion material. The TTL meter in the camera will turn the flash off when enough light has reached the sensor.
Lighting is the most important and creative part of any kind of photography.

Focus

With a depth of field of around one millimeter for precise macro work, camera positioning and focus become critical. If you have a good tripod and head, you'll find that you have at least 10 controls to adjust. Each of them will move the camera. None of them will move the camera along the axis that you care about.
That's why people buy macro focusing rails, e.g., Adorama Macro Focusing Rail . These are little rack and pinions capable of moving the entire camera/lens assembly forward and back. You use the tripod to roughly position the camera/lens and then the macro rail to do fine positioning.
The photos below are snapshots from the garden of the Getty Center. They were taken with a fancy Canon EF 180mm f3.5L Macro USM , but without a tripod.